OPTIMIZATION MODEL OF THE STOMATAL REGULATION IN C-3 PLANTS .3. STOMATAL RESPONSE TO VAPOR-PRESSURE DIFFERENCE

The optimization model of the stomatal regulation of photosynthesis [2 9] predicts a simple one-parameter dependence of the CO2 concentration in the intercellular spaces (c(i)) on the ambient CO2 concentration ( c(a)) and leaf to air vapor pressure difference (Delta w), if the inpu t assumptions of the model are fulfilled. This dependence was fulfille d in two plant species, as demonstrated on the basis of literature dat a. A much larger body of the literature data confirmed the dependence c(i)(Delta w) predicted by the model. Sufficient criteria are suggeste d to evaluate adequate fulfillment of the input assumption of the mode l if various sets of the experimental data are used. It is shown that: 1) the predicted optimum dependence c(i)(Delta w) is fulfilled to a d egree no lower than the input assumption; 2) in most cases where the i nput assumption was not fulfilled, the observed dependence c(i)(Delta w) qualitatively obeyed a more general optimization criterion; 3) devi ations from the optimization statement were observed when the environm ental conditions were far from those, to which plants are adapted in t heir habitats. With the same large set of the literature data, the cri terion of water economy was shown to be fulfilled with less accuracy, but is, however, close to that predicted by the optimization model.